Dr. Gérard Destéfanis Profile

Dr. Gérard Destéfanis

at CEA-LETI

SPIE Involvement:

Conference Program Committee | Author

Publications (69)

PROCEEDINGS ARTICLE | November 17, 2017

Development and characterisation of MCT detectors for space astrophysics at CEA

Proc. SPIE. 10563, International Conference on Space Optics — ICSO 2014

KEYWORDS: Readout integrated circuits, Photovoltaics, Liquid phase epitaxy, Sensors, Diffusion, Quantum efficiency, Diodes, Epitaxy, Astrophysics, Standards development

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The Laboratoire Electronique et Traitement de l’Information (LETI) of the Commissariat à l’Energie Atomique (CEA, Grenoble, France) has been involved in the development of infrared detectors based on HgCdTe (MCT) material for over 30 years, mainly for defence and security programs [1]. Once the building blocks are developed at LETI (MCT material process, diode technology, hybridization, …), the industrialization is performed at SOFRADIR (also in Grenoble, France) which also has its own R&D program [2]. In past years, LETI also developed infrared detectors for space astrophysics in the mid infrared range – the long wave detector of the ISOCAM camera onboard ISO – as well as in the far infrared range – the bolometer arrays of the Herschel/PACS photometer unit –, both instruments which were under the responsibility of the Astrophysics department of CEA (IRFU/SAp, Saclay, France). Nowadays, the infrared detectors used in space and ground based astronomical instruments all come from vendors in the US. For programmatic reasons – increase the number of available vendors, decrease the cost, mitigate possible export regulations, …– as well as political ones – spend european money in Europe –, the European Space Agency (ESA) defined two roadmaps (one in the NIR-SWIR range, one in the MWIR-LWIR range) that will eventually allow for the procurement of infrared detectors for space astrophysics within Europe. The French Space Agency (CNES) also started the same sort of roadmaps, as part of its contribution to the different space missions which involve delivery of instruments by French laboratories. It is important to note that some of the developments foreseen in these roadmaps also apply to Earth Observations. One of the main goal of the ESA and CNES roadmaps is to reduce the level of dark current in MCT devices at all wavelengths. The objective is to use the detectors at the highest temperature where the noise induced by the dark current stays compatible with the photon noise, as the detector operating temperature has a very strong impact at system level. A consequence of reaching low levels of dark current is the need for very low noise readout circuits. CEA and SOFRADIR are involved in a number of activities that have already started in this framework. CEA/LETI does the development of the photo-voltaic (PV) layers – MCT material growth, diode technologies–, as well as some electro-optical characterisation at wafer, diode and hybrid component levels, and CEA/IRFU/SAp does all the electro-optical characterisation involving very low flux measurements (mostly dark current measurements). Depending of the program, SOFRADIR can also participate in the development of the hybrid components, for instance the very low noise readout circuits (ROIC) can be developed either at SOFRADIR or at CEA/LETI. Depending of the component specifications, the MCT epitaxy can be either liquid phase (LPE, which is the standard at SOFRADIR for production purposes) or molecular beam (MBE), the diode technology can be n/p (standard at LETI and SOFRADIR) or p/n (under development for several years now) [3], and the input stage of the ROIC can be Source Follower per Detector (SFD for very low flux low noise programs) or Capacitive Trans Impedance Amplifier (CTIA for intermediate flux programs) [4]. This paper will present the different developments and results obtained so far in the two NIR-SWIR and MWIR-LWIR spectral ranges, as well as the perspectives for the near future. CEA/LETI is also involved in the development of MCT Avalanche Photo Diodes (APD) that will be discussed in other papers [5,6].

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PROCEEDINGS ARTICLE | November 17, 2017

Discussion about photodiode architectures for space applications

Proc. SPIE. 10563, International Conference on Space Optics — ICSO 2014

KEYWORDS: Staring arrays, Long wavelength infrared, Mercury cadmium telluride, Diffusion, Quantum efficiency, Doping, Photodiodes, Diodes, Astronomical imaging, Heterojunctions

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Detection for space application is very demanding on the IR detector: all wavelengths, from visible-NIR (2- 3um cutoff) to LWIR (10-12.5um cutoff), even sometimes VLWIR (15um cutoff) may be of interest. Moreover, various scenarii are usually considered. Some are imaging applications where the focal plane array (FPA) is used as an optical element to sense an image. However, the FPA may also be used in spectrometric applications where light is triggered on the different pixels depending on its wavelength. In some cases, star pointing is another use of FPAs where the retina is used to sense the position of the satellite. In all those configurations, we might distinguish several categories of applications: • low flux applications where the FPA is staring at space and the detection occurs with only a few number of photons. • high flux applications where the FPA is usually staring at the earth. In this case, the black body emission of the earth and its atmosphere ensures usually a large number of photons to perform the detection. Those two different categories are highly dimensioning for the detector as it usually determines the level of dark current and quantum efficiency (QE) requirements. Indeed, high detection performance usually requires a large number of integrated photons such that high QE is needed for low flux applications, in order to limit the integration time as much as possible. Moreover, dark current requirement is also directly linked to the expected incoming flux, in order to limit as much as possible the SNR degradation due to dark charges vs photocharges. Note that in most cases, this dark current is highly depending on operating temperature which dominates detector consumption. A classical way to mitigate dark current is to cool down the detector to very low temperatures. This paper won't discuss the need for wavefront sensing where the number of detected photons is low because of a very narrow integration window. Rigorously, this kind of configuration is a low flux application but the need for speed distinguishes it from other low flux applications as it usually requires a different ROIC architecture and a photodiode optimized for high response speed.

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PROCEEDINGS ARTICLE | June 11, 2015

Infrared SWAP detectors: pushing the limits

Proc. SPIE. 9451, Infrared Technology and Applications XLI

KEYWORDS: Staring arrays, Infrared detectors, Thermography, Infrared imaging, Mercury cadmium telluride, Sensors, Manufacturing, Infrared radiation, Standards development, Image quality standards

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PROCEEDINGS ARTICLE | June 11, 2015

Low-dark current p-on-n MCT detector in long and very long-wavelength infrared

Proc. SPIE. 9451, Infrared Technology and Applications XLI

KEYWORDS: Long wavelength infrared, Liquid phase epitaxy, Mercury cadmium telluride, Sensors, Diffusion, Quantum efficiency, Doping, Photodiodes, Infrared radiation, Heterojunctions

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PROCEEDINGS ARTICLE | June 4, 2015

Update on 10µm pixel pitch MCT-based focal plane array with enhanced functionalities

Proc. SPIE. 9451, Infrared Technology and Applications XLI

KEYWORDS: Staring arrays, Readout integrated circuits, Infrared detectors, Signal to noise ratio, Mercury cadmium telluride, Sensors, Image resolution, Image quality, Modulation transfer functions, Analog electronics

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PROCEEDINGS ARTICLE | June 24, 2014

Getting small, new 10µm pixel pitch cooled infrared products

Proc. SPIE. 9070, Infrared Technology and Applications XL

KEYWORDS: Staring arrays, Signal to noise ratio, Infrared imaging, Mid-IR, Imaging systems, Cameras, Sensors, Infrared radiation, Analog electronics, Image quality standards

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PROCEEDINGS ARTICLE | June 24, 2014

Latest developments in the p-on-n HgCdTe architecture at DEFIR

Proc. SPIE. 9070, Infrared Technology and Applications XL

KEYWORDS: Staring arrays, Long wavelength infrared, Mid-IR, Liquid phase epitaxy, Sensors, Diffusion, Doping, Photodiodes, Diodes, Temperature metrology

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PROCEEDINGS ARTICLE | October 25, 2013

Large format, small pixel pitch and hot detectors at SOFRADIR

Proc. SPIE. 8896, Electro-Optical and Infrared Systems: Technology and Applications X

KEYWORDS: Staring arrays, Infrared detectors, Infrared sensors, Mid-IR, Indium gallium arsenide, Sensors, Infrared radiation, Infrared technology, Medium wave, Quantum well infrared photodetectors

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PROCEEDINGS ARTICLE | June 18, 2013

MCT planar p-on-n LW and VLW IRFPAs

Proc. SPIE. 8704, Infrared Technology and Applications XXXIX

KEYWORDS: Staring arrays, Readout integrated circuits, Long wavelength infrared, Liquid phase epitaxy, Mercury cadmium telluride, Sensors, Diffusion, Photodiodes, Transmission electron microscopy, Neodymium

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In this paper, we report on results obtained both at CEA/LETI and SOFRADIR on p-on-n HgCdTe (MCT) grown by liquid phase epitaxy (LPE) Infra-Red Focal Plane Arrays (IR FPAs) for the Long-wave (LW) and the Very-long-wave (VLW) spectral ranges. For many years, p-on-n arsenic-ion implanted planar technology has been developed and improved within the framework of the joint laboratory DEFIR. Compared to n-on-p, p-on-n technology presents lower dark current and series resistance. Consequently, p-on-n photodiodes are well-adapted for very large FPAs operating either at high temperature or very low flux. The long wave (LW) spectral ranges have been firstly addressed with TV/4, 30 µm pitch FPAs. Our results showed state-of-the-art detector performances, consistent with "Rule 07" law [1], a relevant indicator of the maturity of photodiode technology. The low dark current allows increasing the operating temperature without any degradation of the performances. The subsequent development of p-on-n imagers has produced more compact, less energy consuming systems, with a substantial resolution enhancement. Space applications are another exciting but challenging domains and are good candidates for the p-on-n technology. For this purpose, TV/4 arrays, 30 µm pixel pitch, have been manufactured for the very long wave spectral range. For this detection range, the quality of material and reliability of technology are the most critical. Detectors with different cutoff wavelength have been manufactured to aim 12.5 µm at 78K, 12.5 µm at 40K and 15 µm at 78K. Electro-optical characterizations reveal homogeneous imagers with excellent current operabilities (over 99.9% at best). The results highlight the very good quality of p-on-n technology with carrier diffusion limited dark current, fitting the "Rule 07" law, and high quantum efficiency. Further process developments have been made to improve photodiodes performances. Especially the transition temperature where the dark current shifts from diffusion limited regime to another one, has been lowered by more than 10K. Extremely low dark current has been obtained, down to 50 e-/s/pixel.

PROCEEDINGS ARTICLE | June 11, 2013

High-performance and long-range cooled IR technologies in France

Proc. SPIE. 8704, Infrared Technology and Applications XXXIX

KEYWORDS: Staring arrays, Infrared detectors, Signal to noise ratio, Infrared sensors, Mid-IR, Avalanche photodetectors, Sensors, Infrared radiation, Infrared technology, Medium wave

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PROCEEDINGS ARTICLE | November 19, 2012

Overview of p-on-n planar IRFPAs at DEFIR

Proc. SPIE. 8533, Sensors, Systems, and Next-Generation Satellites XVI

KEYWORDS: Staring arrays, Long wavelength infrared, Mid-IR, Short wave infrared radiation, Mercury cadmium telluride, Imaging systems, Ions, Photodiodes, Neodymium, Medium wave

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In this paper, we report on results obtained both at CEA/LETI and SOFRADIR on p-on-n Infra-Red Focal Plane Arrays (IR FPAs) from the Short-Wave (SW) to the Very-Long-Wave (VLW) spectral range. For many years, p-on-n arsenicion implanted planar technology has been developed and improved within the framework of the joint laboratory DEFIR, a collaborative effort bringing together the expertise of both teams. Compared to n-on-p architecture, p-on-n technology allows to lower dark current density and series resistance by means of respectively long-lifetime minority carriers (hole) and high-mobility majority carriers (electrons). As a consequence, p-on-n photodiodes are well-adapted for very large FPAs operating either at high temperature or very low flux. The Mid-Wave (MW) and Long-Wave (LW) spectral ranges have been firstly addressed with TV/4 FPAs, 30 μm pitch, principally for defence and security applications. Our results showed state-of-the-art detector performances, consistent with “Rule 07” model, a relevant indicator of the p-on-n technology maturity. The subsequent developments of p-on-n imagers have produced more compact, less energy consuming systems, with a substantial resolution enhancement. In this way, MW and LW FPAs, TV format, with 15 μm pixel pitch have been designed. First results obtained in MW (λc=5.3 μm @80 K) for High Operating Temperature (HOT) applications have showed highly promising Electro-Optical (EO) performances. Space applications are another exciting but challenging domains where p-on-n is a good candidate. In this way, imagers dedicated to low-flux detection have first been realized as TV/4 FPAs, with 15μm pitch in the SW spectral range (2 μm). The dark currents obtained are coherent with those published in the literature. Finally, TV/4 arrays, 30 μm pixel pitch, have been manufactured for the very long wave spectral range. For this detection range, the quality of material and reliability of technology are the most critical. The measured dark current fits “Rule 07” well, with homogeneous imagers. In conclusion, DEFIR team have developed, improved and characterized p-on-n IR FPAs from SW to VLW spectral range. In all spectral ranges, we have demonstrated state-of-the-art results, which highlight the quality of material and viability of our p-on-n technology. This technology, currently industrialized by SOFRADIR, opens new ways for next generation of imagers.

PROCEEDINGS ARTICLE | November 19, 2012

Evaluation of very long wave p-on-n MCT FPAs for space applications

Proc. SPIE. 8533, Sensors, Systems, and Next-Generation Satellites XVI

KEYWORDS: Staring arrays, Readout integrated circuits, Liquid phase epitaxy, Sensors, Manufacturing, Doping, Photodiodes, Capacitance, Arsenic, Temperature metrology

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PROCEEDINGS ARTICLE | November 8, 2012

High-performance MCT and QWIP IR detectors at Sofradir

Proc. SPIE. 8541, Electro-Optical and Infrared Systems: Technology and Applications IX

KEYWORDS: Staring arrays, Readout integrated circuits, Infrared detectors, Mid-IR, Avalanche photodetectors, Sensors, Infrared technology, Medium wave, Quantum well infrared photodetectors, Standards development

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PROCEEDINGS ARTICLE | October 24, 2012

Latest developments of MCT focal plane arrays in France

Proc. SPIE. 8541, Electro-Optical and Infrared Systems: Technology and Applications IX

KEYWORDS: Staring arrays, Infrared detectors, Avalanche photodetectors, Sensors, Manufacturing, Photodiodes, Diodes, Epitaxy, Infrared technology, Temperature metrology

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PROCEEDINGS ARTICLE | September 13, 2012

Advances in detector technologies for visible and infrared wavefront sensing

Proc. SPIE. 8447, Adaptive Optics Systems III

KEYWORDS: CMOS sensors, Avalanche photodetectors, Imaging systems, Cameras, Sensors, Quantum efficiency, Wavefront sensors, Adaptive optics, Infrared radiation, Charge-coupled devices

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The purpose of this paper is to give an overview of the state of the art wavefront sensor detectors developments held in Europe for the last decade. The success of the next generation of instruments for 8 to 40-m class telescopes will depend on the ability of Adaptive Optics (AO) systems to provide excellent image quality and stability. This will be achieved by increasing the sampling, wavelength range and correction quality of the wave front error in both spatial and time domains. The modern generation of AO wavefront sensor detectors development started in the late nineties with the CCD50 detector fabricated by e2v technologies under ESO contract for the ESO NACO AO system. With a 128x128 pixels format, this 8 outputs CCD offered a 500 Hz frame rate with a readout noise of 7e-. A major breakthrough has been achieved with the recent development by e2v technologies of the CCD220. This 240x240 pixels 8 outputs EMCCD (CCD with internal multiplication) has been jointly funded by ESO and Europe under the FP6 programme. The CCD220 and the OCAM2 camera that operates the detector are now the most sensitive system in the world for advanced adaptive optics systems, offering less than 0.2 e readout noise at a frame rate of 1500 Hz with negligible dark current. Extremely easy to operate, OCAM2 only needs a 24 V power supply and a modest water cooling circuit. This system, commercialized by First Light Imaging, is extensively described in this paper. An upgrade of OCAM2 is foreseen to boost its frame rate to 2 kHz, opening the window of XAO wavefront sensing for the ELT using 4 synchronized cameras and pyramid wavefront sensing. Since this major success, new developments started in Europe. One is fully dedicated to Natural and Laser Guide Star AO for the E-ELT with ESO involvement. The spot elongation from a LGS Shack Hartman wavefront sensor necessitates an increase of the pixel format. Two detectors are currently developed by e2v. The NGSD will be a 880x840 pixels CMOS detector with a readout noise of 3 e (goal 1e) at 700 Hz frame rate. The LGSD is a scaling of the NGSD with 1760x1680 pixels and 3 e readout noise (goal 1e) at 700 Hz (goal 1000 Hz) frame rate. New technologies will be developed for that purpose: advanced CMOS pixel architecture, CMOS back thinned and back illuminated device for very high QE, full digital outputs with signal digital conversion on chip. In addition, the CMOS technology is extremely robust in a telescope environment. Both detectors will be used on the European ELT but also interest potentially all giant telescopes under development. Additional developments also started for wavefront sensing in the infrared based on a new technological breakthrough using ultra low noise Avalanche Photodiode (APD) arrays within the RAPID project. Developed by the SOFRADIR and CEA/LETI manufacturers, the latter will offer a 320x240 8 outputs 30 microns IR array, sensitive from 0.4 to 3.2 microns, with 2 e readout noise at 1500 Hz frame rate. The high QE response is almost flat over this wavelength range. Advanced packaging with miniature cryostat using liquid nitrogen free pulse tube cryocoolers is currently developed for this programme in order to allow use on this detector in any type of environment. First results of this project are detailed here. These programs are held with several partners, among them are the French astronomical laboratories (LAM, OHP, IPAG), the detector manufacturers (e2v technologies, Sofradir, CEA/LETI) and other partners (ESO, ONERA, IAC, GTC). Funding is: Opticon FP6 and FP7 from European Commission, ESO, CNRS and Université de Provence, Sofradir, ONERA, CEA/LETI and the French FUI (DGCIS).